Tether clamping assemblies and related methods and apparatus

ABSTRACT

Tether clamping assemblies, such as clamping assemblies used to clamp a tether about a spinal feature to assist in spinal fixation, and related methods and systems. In some embodiments, the assembly may comprise a tether configured to engage a bone or other anatomical feature, an inner coupling piece, and an outer coupling piece. A first passage may be at least partially defined by an inner surface of the outer coupling piece and an outer surface of the inner coupling piece. The first passage may be configured such that the tether can be clamped in between the inner surface and the outer surface to allow the tether to move through the first passage in a first direction and lock the tether in place. The inner and outer surfaces preferably differ in surface roughness to facilitate automatic or self-locking of the tether in the assembly.

SUMMARY

Disclosed herein are various embodiments of tether clamping assemblies,along with related bone fixation assemblies with which the tetherclamping assemblies may be used, along with various other inventivemethods and devices. In preferred embodiments, the tether clampingassemblies may be configured to both receive and lock one or more tetherportions therein and also to be coupled with a fixation member, such asan elongated rod. Thus, the inventive devices, features, and methodsdisclosed herein may be particularly suitable for use in connection withspinal fixation. However, it is contemplated that the inventivefeatures, and methods disclosed herein may also be used in other medicalimplants and/or devices, as disclosed in greater detail below.

In a more particular example of a spinal fixation assembly according tosome embodiments, the assembly may comprise a tether configured toengage a spinal feature of a patient's spine, such as a spinous process,transverse process, and/or spinal lamina. In some embodiments, thetether may be devoid of locking teeth. Thus, in some such embodiments,the tether may be smooth, or at least substantially smooth. In someembodiments, the tether may comprise a flattened tether having arectangular cross-sectional shape. In some embodiments, the tether maycomprise opposing surfaces that are at least substantially uniform inroughness. In some such embodiments, both opposing surfaces may besmooth, or at least substantially smooth.

The spinal fixation assembly may further comprise a tether clampingassembly, which may comprise a first coupling piece and a secondcoupling piece configured to be coupled with the first coupling piece.In some such embodiments, the the first coupling piece may comprise aninner coupling piece, the second coupling piece may comprise an outercoupling piece, and the inner coupling piece may be configured to benested or otherwise received within the outer coupling piece.

The tether clamping assembly may comprise a first passage configured toreceive a first portion of the tether. One or both passages may beconfigured to provide for a wedge lock of the tether therein. This maybe provided, for example, by providing opposing surfaces defining thepassage(s), which surfaces may be part of inner and outer surfaces of anouter and inner coupling piece of the assembly, respectively, that aretapered in the same direction relative to a central axis of the tetherclamping assembly, which may coincide with the axis of a cap and/or setscrew in some embodiments. In some embodiments, the respective angles ofthe two surfaces may differ slightly to enhance this wedge lock.Alternatively, however, the two surfaces may taper at the same, or atleast substantially the same, angle.

In some embodiments, the first passage may be defined by a first surfaceand a second surface, wherein the first surface comprises a surfaceroughness greater than a surface roughness of the second surface, andwherein the first passage is configured such that the tether can beclamped in between the first surface and the second surface so as toallow the tether to move through the first passage in a first directionand lock the tether in place so as to at least substantially prevent thetether from moving through the first passage in a second directionopposite from the first direction.

Some embodiments may further comprise a second passage configured toreceive a second portion of the tether to define a tether loop forengaging the spinal feature. In some such embodiments, the secondpassage may also be defined by a first surface and a second surface,wherein the first surface of the second passage comprises a surfaceroughness greater than a surface roughness of the second surface of thesecond passage.

In some embodiments, the first surface of one or both passages may beformed on an inner wall of the outer coupling piece, and the secondsurface may be formed on an outer wall of the inner coupling piece. Toprovide a desired surface roughness differential between the twoopposing surfaces of one or both of the passages, the first surface maycomprise a plurality of projections configured to engage the tether. Theplurality of projections may be defined by, for example, a plurality ofelongated grooves and/or a plurality of teeth. In some embodiments, thesecond surface of one or both passages may be smooth.

In another specific example of a tether clamping assembly according tosome embodiments, the assembly may comprise a tether configured toengage a bone, such as a portion of a patient's spine. The assembly mayfurther comprise an inner coupling piece and an outer coupling piececonfigured to receive the inner coupling piece. A first passage may beat least partially defined by an inner surface of the outer couplingpiece and an outer surface of the inner coupling piece and configured toreceive the tether therethrough. The first passage may be configuredsuch that the tether can be clamped in between the inner surface and theouter surface so as to allow the tether to move through the firstpassage in a first direction and lock the tether in place so as to atleast substantially prevent the tether from moving through the firstpassage in a second direction opposite from the first direction.Preferably at least one of the inner surface and the outer surfacecomprises a plurality of projections configured to engage the tether.Alternatively, one of the inner surface and the outer surface mayotherwise be contoured and/or surface roughened to provide a frictionaldifferential.

In some embodiments, only one of the inner surface and the outer surfacecomprises a plurality of projections configured to engage the tether.

Some embodiments may further comprise a second passage at leastpartially defined by an inner surface of the outer coupling piece and anouter surface of the inner coupling piece. The second passage may beconfigured to receive a second portion of the tether therethrough so asto define a tether loop for engaging the bone. Similar to the firstpassage, in some embodiments, the second passage may be configured suchthat the tether can be clamped in between the inner surface of thesecond passage and the outer surface of the second passage so as toallow the tether to move through the second passage in a first directionand lock the tether in place so as to at least substantially prevent thetether from moving through the second passage in a second directionopposite from the first direction.

Some embodiments may further comprise a cap. In some such embodiments,the cap may be configured to engage the inner coupling piece, such as bythreadably engaging the inner coupling piece. In some embodiments inwhich the cap is threaded, the cap may be configured to engage athreaded opening formed on the inner coupling piece. The cap may also,or alternatively comprise a flange, which may be configured to engagethe outer coupling piece.

In a specific example of method for fixation of a tether to ananatomical feature, the method may comprise extending a flexible tetherin a loop around an anatomical feature of a patient, such as a spinalfeature. An elongate member, such as a rod, may be coupled with aclamping assembly. A first end of the flexible tether may be threadedthrough a first passage of the clamping assembly. The first passage maybe defined by a first pair of opposing surfaces, preferably havingdistinct surface roughnesses. In some implementations, a second end ofthe flexible tether opposite from the first end may be threaded througha second passage defined by a second pair of opposing surfaces alsopreferably having distinct surface roughnesses. In some implementations,the steps of threading the first end of the flexible tether through thefirst passage and threading the second end of the flexible tetherthrough the second passage lock the flexible tether in place about theanatomical feature without use of a secondary locking feature and/orstep to prevent a size of the loop from increasing.

In some implementations, the clamping assembly may comprise an innercoupling piece and an outer coupling piece configured to receive theinner coupling piece. In some such implementations, one or both of thefirst passage and the second passage may be at least partially definedby an inner surface of the outer coupling piece and an outer surface ofthe inner coupling piece.

In some implementations in which the elongate member comprises a rod,the inner coupling piece may comprise a slot configured to receive andengage the rod. Thus, in some such implementations, the step of couplingthe elongate member with the clamping assembly may comprise engaging therod with the slot.

The features, structures, steps, or characteristics disclosed herein inconnection with one embodiment may be combined in any suitable manner inone or more alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the disclosure aredescribed, including various embodiments of the disclosure withreference to the figures, in which:

FIG. 1 is an exploded, perspective view of a spinal fixation assemblyincluding a tether clamping assembly according to some embodiments;

FIG. 2A is an exploded, side elevation view of the spinal fixationassembly of FIG. 1;

FIG. 2B is a cross-sectional view of the spinal fixation assembly ofFIG. 2A;

FIG. 3 is a perspective view of an inner coupling piece of a tetherclamping assembly according to some embodiments;

FIG. 4 is a side elevation view of the inner coupling piece of FIG. 3;

FIG. 5 is a perspective view of an outer coupling piece of a tetherclamping assembly according to some embodiments;

FIG. 6 is a side elevation view of the outer coupling piece of FIG. 5;

FIG. 7 is a perspective view of a threaded cap that may be used inconnection with one or more of the tether clamping assemblies disclosedherein;

FIG. 8 is a perspective view of a tether clamping assembly according tosome embodiments;

FIG. 9 is a perspective view of a spinal fixation assembly including atether clamping assembly according to another embodiment;

FIG. 10 is a perspective view of the inner coupling piece of the tetherclamping assembly of FIG. 9;

FIG. 11 is a perspective view of the outer coupling piece of the tetherclamping assembly of FIG. 9;

FIG. 12 is a perspective view of a tether clamping assembly according tostill another embodiment;

FIG. 13 is a perspective view of the inner coupling piece of the tetherclamping assembly of FIG. 12;

FIG. 14 is a perspective view of the outer coupling piece of the tetherclamping assembly of FIG. 12;

FIG. 15 is a perspective view of an alignment insert configured to beused in connection with the tether clamping assembly of FIG. 12;

FIG. 16 is a perspective view of a one-piece tether clamping assemblyaccording to some embodiments;

FIG. 17 is a side elevation view of the tether clamping assembly of FIG.16; and

FIG. 18 is a cross-sectional view of the tether clamping assembly ofFIGS. 16 and 17.

DETAILED DESCRIPTION

A detailed description of apparatus, systems, and methods consistentwith various embodiments of the present disclosure is provided below.While several embodiments are described, it should be understood thatthe disclosure is not limited to any of the specific embodimentsdisclosed, but instead encompasses numerous alternatives, modifications,and equivalents. In addition, while numerous specific details are setforth in the following description in order to provide a thoroughunderstanding of the embodiments disclosed herein, some embodiments canbe practiced without some or all of these details. Moreover, for thepurpose of clarity, certain technical material that is known in therelated art has not been described in detail in order to avoidunnecessarily obscuring the disclosure.

Apparatus, methods, and systems are disclosed herein relating to spinalfixation or other bone fixation. In some embodiments, tether clampingassemblies may be provided, such as clamping assemblies used to clamp atether about a spinal feature to assist in spinal fixation. Moreparticularly, in some embodiments, a tether clamping assembly may alsobe configured to engage a spinal fixation rod. In preferred embodiments,the clamping assembly may be configured such that one or more portionsof a tether may be self-locked therein without requiring any additionallocking elements, features, or steps. In this manner, for example, atether may be looped around a spinal feature or other anatomicalfeature, coupled with a fixation element, such as a rod, and then lockedin place to stabilize the anatomical feature.

The embodiments of the disclosure may be best understood by reference tothe drawings, wherein like parts may be designated by like numerals. Itwill be readily understood that the components of the disclosedembodiments, as generally described and illustrated in the figuresherein, could be arranged and designed in a wide variety of differentconfigurations. Thus, the following detailed description of theembodiments of the apparatus and methods of the disclosure is notintended to limit the scope of the disclosure, as claimed, but is merelyrepresentative of possible embodiments of the disclosure. In addition,the steps of a method do not necessarily need to be executed in anyspecific order, or even sequentially, nor need the steps be executedonly once, unless otherwise specified. Additional details regardingcertain preferred embodiments and implementations will now be describedin greater detail with reference to the accompanying drawings.

FIG. 1 is an exploded view of a spinal fixation assembly 100 accordingto some embodiments. Assembly 100 comprises a tether 110 that isconfigured to engage a spinal feature of a patient's spine, such as, inpreferred embodiments, looped around the spinal lamina and/or otherspinal features, such as the transverse processes of the patient'sspine. Tether 110 in some embodiments, may comprise a flat, flexibleband resembling, for example, a piece of tape. In preferred embodiments,tether 110 may be flat and/or smooth on both opposing sides. Forexample, in preferred embodiments tether 110 may be devoid of lockingteeth and/or other projections.

Assembly 100 further comprises a tether clamping assembly 130 configuredto engage and couple a coupling member, such as a rod 120 or otherelongate member, with the tether 110 so as to facilitate coupling of apatient's spine in a desired position without use of pedicle screws orother similar bone-invasive components. Assembly 100 further comprises acap 160 configured to engage tether clamping assembly 130, as describedin greater detail below. Although preferred embodiments disclosedherein, including assembly 100, may be configured to allow for couplingof a tether with spinal features, it is contemplated that the inventiveprinciples disclosed herein may be applied to provide forclamping/securing of a tether to other anatomical features, such assecuring two portions of a broken or cracked bone, such as a femur, forexample. In some such embodiments not involving spinal anatomy, thespinal rod or other fixation member discussed below may be omitted. Insome such embodiments, the bone itself may be clamped by the clampingassembly 130 instead of clamping both the tether and the rod/fixationmember.

FIG. 2A is a side elevation view of spinal fixation assembly 100. Asshown in this figure, tether clamping assembly 130 comprises twoseparate pieces, namely, a first or inner coupling piece 140 and asecond or outer coupling piece 150 configured to be coupled with thefirst coupling piece 140.

First/inner coupling piece 140 defines a slot 145 for receipt of a rod120 or other elongate and/or rigid coupling member therethrough.Preferably, slot 145 is shaped to match, or at least substantiallymatch, the shape of the outer surface of rod 120 such that rod 120 maybe firmed engaged/gripped by slot 145. In some embodiments, slot 145 maycomprise a plurality of engagement features 141, such as teeth, grooves,spikes, or a contoured and/or roughened surface to further facilitate afirm engagement between rod 120 and inner coupling piece 140. Thisroughening may be applied, in some embodiments, by way of diamondplating, blasting, etc. In some embodiments, one or both of the couplingpieces may comprise features that allow for slot 145 to resiliently flexto receive rod 120 therein and then snap back in place to fixedly engagerod 120, as discussed in greater detail below.

In embodiments providing a snap-on feature, slot 145 may also beroughened, textured, and or provided with teeth or other engagementfeatures 141, as mentioned above. In this manner, the inner couplingpiece 140 may be snapped onto the rod 120 and the inner coupling piece140 may be held in place on the rod without requiring a practitioner tohold it in place by virtue of the engagement features 141 and/or atextured or roughened surface. However, in order to allow the innercoupling piece 140 to be slid to its desired location on the rod 120, itmay be preferred that the frictional engagement be configured so as toallow a practitioner to manually overcome the friction to move the innercoupling piece 140 and/or assembly 100 as needed during surgery.

FIG. 2B is a cross-sectional view of spinal fixation assembly 100. Asdepicted in this figure, first/inner coupling piece 140 is configured tobe received within second/outer coupling piece 150 in a nesting fashion.In some embodiments, including the depicted embodiment, first/innercoupling piece 140 is configured to be wholly received withinsecond/outer coupling piece 150. However, it is contemplated that, inother embodiments, a portion of the outer coupling piece may protrudefrom the inner coupling piece or, as discussed in connection withanother embodiment below, tether clamping assembly 130 may insteadcomprise a single element.

Second/outer coupling piece 150 may similarly comprise a slot 155 thatmay be configured to be aligned with slot 145 upon coupling innercoupling piece 140 with outer coupling piece 150. By coupling innercoupling piece 140 with outer coupling piece 150, a pair of opposingpassages are defined for receipt of separate portions of tether 110therethrough.

Thus, first and second passages may be defined, respectively, by aninner surface 152 of outer coupling piece 150 and an outer surface 142of inner coupling piece 140, both of which may be configured to receiveseparate portions of tether 110 therethrough. In preferred embodiments,clamping assembly 130 is self-locking. In other words, by advancingtether 110 through one or both passages, the tension on tether 110 aloneresults in a tightening, and preferably a locking, of tether 110 inclamping assembly 130.

Preferably, clamping assembly 130 is configured such that tether 110 canbe clamped and/or locked in clamping assembly 130 so as to allow tether110 to move through one or both passages in a first direction to lockthe tether in place but so as to prevent, or at least substantiallyprevent, tether 110 from moving through one or both passages in a seconddirection opposite from the first direction. Thus, with respect to theview of FIGS. 2A and 2B, tether 110 may be advanced in an upwarddirection along both opposing passages, thereby resulting in a tetherloop (see FIG. 1) that gets smaller, but may be prevented, or at leastsubstantially prevented, from being advanced in a downward direction.Thus, upon applying a force to tether 110 in the upward direction, theloop locks in place, preferably about a spinal feature. In someembodiments, the greater the force applied in a locking direction, thetighter the lock, and therefore the more difficult it is to move thetether in an opposite direction from the locking direction.

In the depicted embodiment, this self-locking feature may be enhanced byproviding a friction differential between the two opposing surfacesthrough which one or more portions of tether 110 are received.Preferably, this friction differential is applied such that a movablesurface has a greater surface roughness than an opposing non-movablesurface. Because, as discussed in greater detail below, in someimplementations of inventive methods disclosed herein, the innercoupling piece 140 may be coupled with a rod 120 or other elongatemember prior to coupling outer coupling piece 150 with inner couplingpiece 140, outer coupling piece 150 may be considered the “moveable”element of clamping assembly 130.

Thus, for example, as depicted in FIG. 2B, inner surface(s) 152 of outercoupling piece 150 comprises a plurality of projections 153. In someembodiments, projections 153 may be defined by a plurality of elongatedgrooves formed on the inner surface 152 of outer coupling piece 150.However, alternative embodiments are contemplated in which projections153 may comprise, for example, teeth. As still another alternative,inner surface 152 of outer coupling piece 150 may, in some embodiments,lack deliberately formed projections and may instead simply comprise aroughened surface. Outer surface(s) 142 of inner coupling piece 140 may,in some embodiments, comprise a smooth surface. However, so long as afriction differential is provided, whether by providing projections 153or otherwise, outer surface(s) 142 need not be smooth in someembodiments. Surfaces 142 and 152, along with their respective surfacefeatures, are therefore an example of means for self-locking a tetherwithin a rod-coupling assembly.

It is also contemplated, however, that, in some embodiments, suitablelocking may be provided without providing the friction differentialdescribed above. For example, the embodiment depicted in FIG. 2B alsoprovides for self-locking of tether 110 by virtue of a wedge-lockingfeature. Thus, although it may be preferred to have the two opposingsurfaces 142/152 have a friction differential, this may be omitted incertain contemplated embodiments. In embodiments in which these twosurfaces are identical, or at least substantially identical, it is alsopreferred that both surfaces be roughened, contoured, and/or formed withfrictional features, such as teeth or protrusions, for example. However,it is also contemplated that for certain applications opposing surfaces142/152 may instead both be smooth.

Because of the unique design of assembly 100, locking of tether 110 mayalso result in further locking/tightening of the grip on rod 120. Forexample, due to the wedging of outer coupling piece 150 onto innercoupling piece 140, as the tension on tether 110 is increased in thetightening direction by pulling one or both ends of tether 110 throughthe two opposing passages defined by outer coupling piece 150 and innercoupling piece 140, not only is tether 110 pinched more tightlytherebetween to prevent it from being loosened, but, at the same time,the slot 145 created by the inner surface of inner coupling piece 140 issqueezed against the rod 120 more tightly to further lock the tetherclamping assembly 130 in place with respect to the rod 120. This featureis provided for by virtue of the wedge lock previously described, inwhich two tapering surfaces are wedged against each other (with thetether 110 therebetween) in combination with making the inner couplingpiece 140 flexible so that the size of slot 145 can vary to facilitatethis compression. Preferably, as shown in the depicted embodiment, thesetapering surfaces are frusto-conical surfaces.

Other aspects/features of spinal fixation assembly 100 can be seen inFIGS. 3-8. For example, as shown in FIG. 3, inner coupling piece 140 maycomprise a central opening 147, which may be threaded to receive cap160. Opening 147 may be configured to be aligned with opening 157 ofouter coupling piece 150, as shown in FIG. 5, upon coupling of outercoupling piece 150 with inner coupling piece 140. Although preferablyopenings 147 and 157 are configured to be aligned when outer couplingpiece 150 is coupled with inner coupling piece 140, opening 157 need notbe threaded since threaded opening 147 may engage cap 160 and therebyengage outer coupling piece 150 without itself requiring a directthreaded connection with cap 160.

Inner coupling piece 140 may further comprise opposing grooves 144.Grooves 144 may be provided in order to increase the flexibility of slot145. For example, as previously mentioned, slot 145 may be configured toexpand to receive rod 120 and then resiliently snap back in place to atleast partially envelop rod 120, which functionality may be provided bygrooves 144. In some embodiments, grooves 144 may also, oralternatively, be used to provide locations to facilitategripping/engagement by an instrument that may be used to installcoupling piece 140 and/or hold coupling piece 140 in place during one ormore stages of a surgical procedure.

As also better seen in FIG. 4, inner coupling piece 140 may compriseopposing outer surfaces 142A and 142B, each of which may partiallydefine a separate tether passage. As previously mentioned, preferably,outer surfaces 142A and 142B are smooth or at least have surfaceroughnesses that are less than that of respective opposing surfaces,which may be defined by outer coupling piece 150, that, together withouter surfaces 142A and 142B, define opposing tether passages.Similarly, FIG. 4 better depicts opposing grooves 144A and 144B, whichdirectly extend from opposing outer surfaces 142A and 142B,respectively. As best shown in this figure, grooves 144A and 1446,together with slot 145, form opposing narrowed portions that provide theaforementioned flexibility and/or provide engagement locations for asuitable instrument.

FIG. 5 is a perspective view of outer coupling piece 150. As best seenin this figure, the upper portion of outer coupling piece 150 maycomprise one or more features to facilitate desired functionality. Forexample, as previously mentioned an opening 157 may be provided toreceive a threaded projection or another projection from a cap and/orset screw. In addition, opening 157 need not be threaded, but may bedefined by a plate 151 configured to engage a portion of inner couplingpiece 140 that defines a threaded opening 147 configured to be alignedwith opening 157 such that inner coupling piece 140 can extend into butcannot extend out of the opposite end of outer coupling piece 150. Plate151 may also be configured to provide a surface upon which a flangedportion 164 of cap 160 may rest and/or pinch a portion of tether 110, asdiscussed in greater detail below.

Plate 151 may further define opposing tether openings 156A and 156B. Inembodiments using a tether having an elongated, rectangularcross-section, such as tether 110, tether openings 156A and 156B mayhave a similar matching shape such that the tether may snap into placewhen properly oriented within the opposing passages, the openings at oneend of which are defined by tether openings 156A and 156B.

Tether openings 156A and 156B may be partially defined by four corners158 that are positioned along the portion of outer coupling piece 150defining opening 157. Corners 158 are defined by opening 157 along withrespective walls that extend parallel to slit 155 (and therefore extendparallel to an axis defined by a rod positioned therein). These tetheropenings 156A/156B may be useful in allowing the tether to be held inplace temporarily (before locking/clamping) to allow a practitioner toperform other tasks while awaiting finalization of theinstallation/surgery.

As also shown in FIG. 5, opposing slits 159A and 159B may be formedadjacent to plate 151. As best seen in FIG. 8, which depicts assembly130 with cap 160 in place, slits 159A and 1596 may, together withflanged portion 164 of cap 160, define opposing apertures through whichopposing portions of tether 110 may exit from opposing sides of assembly130.

Some embodiments may further comprise one or more features to facilitateengagement with a suitable instrument. Thus, for example, outer couplingpiece 150 comprises a notch 154, which may engage a correspondingprotruding element of a suitable surgical instrument. Although notvisible in FIG. 5, in some embodiments, a similar notch may be formed onthe opposite side of outer coupling piece 150.

FIG. 6 more clearly depicts projections 153 formed within curved innersurface 152A of outer coupling piece 150. As shown in this figure,projections 153 may be formed by cutting elongated, parallel grooveswithin inner surface 152A. Although not visible in FIG. 6, as previouslymentioned, in preferred embodiments, the opposing inner surfacesimilarly comprises a plurality of projections 153 to facilitate theself-locking feature of assembly 130.

FIG. 7 is a perspective view of a cap 160 of spinal fixation assembly100 according to some embodiments. Cap 160 comprises a flanged portion164, which may be configured to engage an upper surface of outercoupling piece 150, such as plate 151. Cap 160 further comprises a malethreaded portion 162 and a keyed slot 161. As previously mentioned, malethreaded portion 162 may be configured to engage female threads of innercoupling piece 140 and outer coupling piece 150 may be clampedtherebetween. Keyed slot 161 may be configured to engage an instrument,such as a driver, used to couple cap 160 to assembly 130.

In some embodiments, a portion or, in some such embodiments, twoopposing portions, of the tether 110 may be clamped in between flangedportion 164 of cap 160 and another portion of assembly 130, such as theledges formed by opposing slits 159A and 159B or plate 151 of outercoupling piece 150. Thus, cap 160 is an example of secondary means forlocking a tether within a rod-coupling assembly. Cap 160 may also servethe function of increasing the lock on the rod and/or tether and/ordecreasing the possibility of unwanted loosening/disassembly.

In addition, providing cap 160 may decrease the possibility of frayedportions of tether 110 from extending down into assembly 130 followingcutting of tether 110. This may allow for cutting of tether 110 closerto assembly 130 than may otherwise be possible or desirable. However, aspreviously explained, self-locking may be provided by the differentialfriction of the opposing surfaces of one or both tether passages oftether clamping assembly 130. Thus, it is contemplated that cap 160 maybe omitted in some embodiments. It is also contemplated that cap 160 maycomprise a set screw lacking a flanged portion in some embodiments.

FIG. 8 is a perspective view of tether clamping assembly 130 showinginner coupling piece 140 fully inserted within outer coupling piece 150and with cap 160 fully engaged with inner coupling piece 140. Althoughnormally a tether would be engaged between opposing surfaces of innercoupling piece 140 and outer coupling piece 150, respectively, in thisconfiguration, tether 110 is omitted from FIG. 8 to allow for betterviewing of certain aspects of assembly 130. Most notably, opposingapertures are depicted that may allow for a tether to exit from oppositesides of assembly 130. These apertures are defined by opposing slits 159(only one of which is visible in FIG. 8), respectively, along with alower surface of flanged portion 164 of cap 160.

Another unique aspect of assemblies 100 and/or 130 is the ability toloosen the grip/lock/clamp on the tether 110 for readjustment. Aspreviously mentioned, locking of the tether may be accomplishedautomatically by engaging the tether 110 between the opposing surfacesof the inner and outer coupling pieces and pulling the tether throughone or both of the openings in the locking direction, with the optionalcap 160 to further enhance this locking of the tether 110 and/or the rod120. This may allow for sequential tightening of various elements of aspinal fixation system without leaving instrumentation in place whilemoving to a new location within the system, which may also reduce theinstrument tray and decrease surgery time.

However, if loosening is needed, the outer coupling piece 150 may beengaged, likely with a suitable instrument, in order to lift the outercoupling piece 150 away from the inner coupling piece 140 slightly,which will release the lock on tether 110 and allow the tether 110 to beloosened. In some embodiments, notch 154 may be configured to engage acorresponding element of a suitable surgical instrument in order tofacilitate this loosening.

FIG. 9 is a perspective view of an alternative embodiment of a spinalfixation assembly 900. Although not depicted in FIG. 9, assembly 900would typically comprise a tether, which may be similar to tether 110,that is configured to engage a spinal feature of a patient's spine, suchas, in preferred embodiments, looped around the spinal lamina and/orother spinal features, such as the transverse processes of the patient'sspine.

Like assembly 100, assembly 900 further comprises a tether clampingassembly 930 configured to engage and couple a coupling member, such asa rod 920 or other elongate member, with a tether so as to facilitatecoupling of a patient's spine in a desired position without use ofpedicle screws or other similar bone-invasive components. Tetherclamping assembly 930 again comprises two separate elements configuredto be coupled with one another so as to clamp one or more (preferablytwo) portions of a tether therein. More particularly, tether clampingassembly 930 comprises an inner coupling piece 940 configured to bereceived within an outer coupling piece 950.

However, tether clamping assembly 930 differs from tether clampingassembly 130 in several ways. For example, as shown in FIGS. 9 and 10,inner coupling piece 940 comprises a pair of removable tabs, namely,tabs 970A and 970B. Tabs 970A and 970B may be configured to facilitatecoupling of outer coupling piece 950 with inner coupling piece 940. Tabs970A and 970B may comprise a plurality of ridges 972.

Each ridge 972, or each pair of adjacent ridges 972, may serve adistinct purpose during the installation process. For example, the toppair of ridges 972 may be used to prevent the outer coupling piece 950from being removed from assembly 930 during, for example, snapping ofthe rod 920 into slot 945. The middle pair of ridges 972 may prevent theouter coupling piece 950 from dropping all of the way down adjacent tothe threaded opening 947 of inner coupling piece 940 to provide spacingfor an instrument or a surgeon's hand during this stage.

Following this stage, the outer coupling piece 950 may be dropped downbelow the lowest pair of ridges to allow for threading of the tetherthrough opposing passages defined by respective inner surfaces of theouter coupling piece 950 and respective, opposing outer surfaces of theinner coupling piece 940, as previously described. After threading thetether through these passages, the tether may be tensioned about aspinal feature and/or bone.

As previously mentioned, preferably tether clamping assembly 930 isconfigured to provide for self-locking of the tether. In other words, insome embodiments, the tether clamping assembly 930 may be configuredsuch that the tether can be clamped in between opposing surfaces so asto allow the tether to move through the passage(s) in a first directionand lock the tether in place so as to, without any further steps orlocking elements/features, at least substantially prevent the tetherfrom moving through the passage(s) in a second direction opposite fromthe first direction. As also previously mentioned, this self-lockingfeature may be provided by providing a friction differential between thetwo opposing surfaces through which one or more portions of the tetherare received. Preferably, this friction differential is applied suchthat a movable surface has a greater surface roughness than an opposingnon-movable surface.

Thus, for example, as depicted in FIGS. 10 and 11, opposing innersurface(s) 952 of outer coupling piece 950 comprises a plurality ofprojections 953, which may be formed by elongated grooves. Outersurface(s) 942 of inner coupling piece 940 may, in some embodiments,comprise a smooth surface, or at least a surface lackingprojections/grooves. However, again, so long as a friction differentialis provided, whether by providing projections 953 or otherwise, outersurface(s) 942 need not necessarily be smooth. Surfaces 942 and 952,along with their respective surface features, are therefore anotherexample of means for self-locking a tether within a rod-couplingassembly.

Once the tether has been suitably tensioned and locked in place, tabs970A and 970B may be removed. In order to facilitate such removal,weakened portions 975, such as frangible weakening lines, may be formedin one or both of tabs 970A and 970B. Inner coupling piece 940 may alsocomprise opposing grooves 944 for increasing the flexibility of slot 945and/or facilitate gripping/engagement by a surgical instrument.

Like outer coupling piece 150, outer coupling piece 950 comprises anopening 957, which may be configured to receive a threaded projection oranother projection from a cap and/or set screw. Opening 957 need not bethreaded but may be configured to be aligned with a threaded opening 947of inner coupling piece 940, as previously described. Outer couplingpiece 950 may further comprise one or more notches 954, which may engagea corresponding protruding element of a suitable surgical instrument.

However, outer coupling piece 950 differs from outer coupling piece 150in several respects. For example, opposing apertures 956 are formed inouter coupling piece (only one of which is visible in FIG. 11) such thata tether (not shown) may extend through the opposing passages previouslymentioned and, instead of exiting from an upper surface, may extendthrough opposing apertures 956 formed in side walls of outer couplingpiece 950.

In addition, instead of comprising opposing slits 159A and 159B in a topsurface of the outer coupling piece, as is the case in outer couplingpiece 150, outer coupling piece 950 comprises opposing slits 959A and959B formed in an inner surface of outer coupling piece 950. Opposingslits 959A and 959B may be configured to partially accommodate ridges972. However, in order to secure outer coupling piece 950 in a desiredposition on tabs 970A/970B, preferably slits 959A/959B are slightlysmaller than ridges 972 such that ridges 972 prevent passage of outercoupling piece 950. Passage of outer coupling piece 950 beyond a givenset of ridges 972 may be accomplished by, for example, flexing tabs970A/970B.

FIG. 12 depicts yet another alternative embodiment of a spinal fixationassembly 1200. Although not depicted in FIG. 12, assembly 1200 wouldtypically comprise a tether, which may be similar to tether 110, that isconfigured to engage a spinal feature of a patient's spine, and anelongated fixation member or other coupling member, such as a rod.

Like assemblies 100 and 900, assembly 1200 comprises a tether clampingassembly 1230 comprising two separate elements configured to be coupledwith one another so as to clamp one or more (preferably two) portions ofa tether and rod or other coupling member therein. More particularly,tether clamping assembly 1230 comprises an inner coupling piece 1240configured to be received within an outer coupling piece 1250, aspreviously described.

However, tether clamping assembly 1230 differs from the tether clampingassemblies previously described in several ways. For example, as shownin FIGS. 12 and 15, tether clamping assembly 1230 comprises an alignmentinsert 1280 that is configured to be received within an opening formedwithin outer coupling piece 1250 and/or inner coupling piece 1240.Alignment insert 1280 may be used to facilitate coupling of outercoupling piece 1250 with inner coupling piece 1240 and/or may be used tofacilitate introduction of a set screw (not shown) into inner couplingpiece 1240. Thus, alignment insert 1280 may comprise a tip 1282, whichmay be configured with a smaller diameter relative to an adjacent bodyportion 1284 so as to allow for receipt of tip 1282 within one or bothof threaded opening 1247 of inner coupling piece 1240 (see FIG. 13) andopening 1257 of outer coupling piece 1250 (see FIG. 14). Opposite fromtip 1282 is a handle 1286, which may be configured to allow a surgeon orpractitioner to push alignment insert 1280 into one or more receivingopenings to facilitate introduction and coupling of a set screw intothreaded opening 1247. A central bore 1285 may be formed in alignmentinsert 1280 and may extend from handle 1286 to tip 1282 to allow for aset screw to travel therethrough. A suitable instrument may also bereceived within bore 1285 to further facilitate such coupling.

A perspective view of the inner coupling piece 1240 is shown in FIG. 13.As shown in this figure, inner coupling piece 1240 comprises a pair ofopposing outer surfaces, namely surfaces 1242A and 1242B. As previouslydiscussed, surfaces 1242A and 1242B, respectively, may be configured todefine one side of a passage for receipt of a tether (not shown)therethrough. As also previously discussed, surfaces 1242A and 1242B arepreferably smooth, or at least having a surface roughness that is lessthan that of the opposing surface(s), which may be defined by an innersurface or surfaces of outer coupling piece 1250.

As also previously discussed, inner coupling piece 1240 may comprise aslot 1245 that is shaped to match, or at least substantially match, theshape of the outer surface of a rod such that the rod may be firmlyengaged/gripped by slot 1245. In some embodiments, slot 1245 maycomprise a plurality of teeth (not shown) or a contoured and/orroughened surface to further facilitate a firm engagement between therod and inner coupling piece 1240. Inner coupling piece 1240 furthercomprises a pair of opposing grooves, namely, grooves 1244A and 1244B,which may increase the flexibility of slot 1245 to allow for receipt ofa rod therein by way of a snap-fit connection. In the depictedembodiment, grooves 1244A and 1244B comprise slits that terminateadjacent to slot 1245.

A perspective view of outer coupling piece 1250 is shown in FIG. 14. Asshown in this figure, outer coupling piece 1250, like inner couplingpiece 1240, may comprise a slot 1255 that may be aligned with slot 1245such that a rod (not shown) or another coupling member may extendthrough a slot defined by slots 1245 and 1255.

As also shown in FIG. 14, opposing apertures 1256A and 1256B are formedin outer coupling piece 1250 such that a tether (not shown) may extendthrough the opposing passages previously mentioned and ultimately extendthrough opposing apertures 1256A and 1256B. Apertures 1256A and 1256Bare formed in opposing shelves 1259A and 1259B of outer coupling piece1250. Shelves 1259A and 1259B may be configured to be aligned, or atleast substantially aligned, with the top surface of inner couplingpiece 1240 upon fully coupling outer coupling piece 1250 with innercoupling piece 1240.

Finally, as previously discussed, outer coupling piece 1250 furthercomprises two internal surfaces each having a plurality of projections1253, which may, in some embodiments, be defined by a series of parallelgrooves, as previously described. These surfaces, together with outersurfaces 1242A and 1242B of inner coupling piece 1240, define twoseparate passages for receipt of opposing portions of a tethertherethrough, as also previously described. The opposing surfaces thatdefine these two passages, along with their respective surface features,are therefore another example of means for self-locking a tether withina rod-coupling assembly.

FIGS. 16-18 depict still another embodiment of a tether clampingassembly 1630 that may be used in connection with a fixation assembly,such as a spinal fixation assembly. Tether clamping assembly 1630 isconfigured to receive two portions of a tether (not shown) therethroughso as to define a loop and tighten the loop around a spinal feature orother anatomical feature, as previously discussed. However, tetherclamping assembly 1630 differs from the other coupling assembliesdescribed herein in that tether clamping assembly 1630 is defined by aunitary structure rather than two separate structures coupled together.More particularly, tether clamping assembly 1630 comprises an internalstructure defined by two locking members 1651A and 1651B.

Locking members 1651A and 1651B are movably (in the depicted embodiment,pivotably) positioned in respective internal chambers so as to defineempty spaces on either side. More particularly, locking members 1651Aand 1651B are positioned in between respective inner spaces 1657A/1657Band outer spaces 1659A/1659B. In the depicted embodiment, opposingtether receiving paths are defined by outer spaces 1659A/1659B, as bestseen in the cross-sectional view of FIG. 18.

Respective outer surfaces of locking members 1651A and 1651B maycomprise a plurality of projections 1653, or may otherwise be surfaceroughened relative to the opposing inner surfaces 1642A and 1642B. Thus,both passages of coupling mechanism 1630 are configured to beself-locking with respect to tether portions received therethrough. Inorder words, upon extending respective tether portions through thesepassages and applying tension in the upward direction (relative to theorientation in FIGS. 16 and 17), the tether portions retain the appliedtension and are prevented, or at least inhibited, from being pulled inthe opposite, downward direction. The opposing surfaces definingpassages 1659A and 1659B, along with their respective surface features,are therefore another example of means for self-locking a tether withina rod-coupling assembly.

Surface 1642A, together with the surface upon which projections 1653Aare formed, define a first passage 1659A for receiving a first portionof a tether, such as a flexible band, therethrough. Similarly, surface1642B, together with the surface upon which projections 1653B areformed, define a second passage 1659B for receiving a second portion ofthe tether therethrough. These passages have openings on opposite endsof tether clamping assembly 1630, namely, upper openings 1656A and 1656Band respective lower openings 1652A and 1652B.

Preferably, locking members 1651A and 1651B are pivotably movable withintheir respective chambers. Thus, outer spaces 1659A/1659B may beconfigured, respectively, to allow locking members 1651A and 1651B to beresiliently biased towards the center of tether clamping assembly 1630by a predetermined distance. Correspondingly, the width of the opposingpassages defined in part by locking members 1651A and 1651B may beslightly increased as locking members 1651A and 1651B pivot in thismanner. In addition, as depicted in the figures, respective baseportions of locking members 1651A and 1651B may be narrowed to providethe flexibility to allow for this pivoting/movement.

Because locking members 1651A and 1651B are movable, as previouslydiscussed, preferably the friction differential between the opposingsurfaces defining the passages are applied such that the surface onlocking members 1651A and 1651B (the movable surfaces) have a greatersurface roughness than the opposing non-movable surfaces. Thus, aspreviously mentioned, the projections 1653 may only be formed on thesesurfaces of locking members 1651A and 1651B and not on the opposinginner surfaces 1642A and 1642B of the inner chamber of tether clampingassembly 1630.

Tether clamping assembly 1630 further comprises release mechanisms toallow the self-locking feature to be unlocked. In the depictedembodiment, these release mechanisms comprise tether clamping assemblyopenings 1658A and 1658B which are positioned to allow access torespective locking member openings 1654A and 1654B formed in uppersurfaces of locking members 1651A and 1651B. As best shown in thecross-sectional view of FIG. 18, openings 1654A and 1654B may beconfigured to receive portions of a suitable instrument, such as prongs.In some embodiments, this may allow a user to, for example, squeeze thelocking members 1651A and 1651B towards one another and thereby releasetheir respective locks on the tether portions extending through thetether passages extending between upper openings 1656A and 1656B andrespective lower openings 1652A and 1652B. Of course, only one of thelocking member openings 1654A and 1654B may be engaged, if desired, inorder to only unlock the locking/clamping of tether clamping assembly1630 on one tether portion instead of both portions extending throughtether clamping assembly 1630.

Various methods for clamping a tether to a spinal feature or otheranatomical feature may also be performed using one or more of theinventive clamping assemblies, or sub-elements of such an assembly,taught herein. For example, in some implementations of such methods, atether, such as in some such implementations a flexible band, may beextended in a loop around an anatomical feature, such as around a spinaltransverse process or spinal lamina, for example. An elongate member,such as a rigid rod, may be coupled with a clamping assembly, such asany of the various clamping assemblies disclosed herein.

A first end of the tether may then be fed through a first passage of theclamping assembly. In some implementations, the first passage may bedefined by a first pair of opposing surfaces having distinct surfaceroughnesses. In some such implementations, a movable surface (relativeto the elongate member) may comprise a greater surface roughness that anopposing non-movable surface. Thus, for example, the movable surface maybe formed with a plurality of grooves and/or projections to increase thesurface roughness and/or grip on the tether.

In some implementations, a second end of the flexible tether oppositefrom the first end may also be fed through a second passage, which maybe defined by a second pair of opposing surfaces also having distinctsurface roughnesses. In some implementations, the first end of theflexible tether may be fed through the first passage and/or the secondend of the flexible tether may be fed through the second passage toautomatically lock the flexible tether in place about the anatomicalfeature without the use of a secondary locking feature, such as alocking cap, set screw, or the like, to prevent a size of the loop fromincreasing.

In some implementations, the clamping assembly may comprise an innercoupling piece and an outer coupling piece configured to receive theinner coupling piece. In some such implementations, the first passageand the second passage may be at least partially defined by an innersurface of the outer coupling piece and an outer surface of the innercoupling piece.

In some implementations, the clamping assembly may also be unlockedfollowing the self-locking procedure. For example, a user may unlock oneor both tether portions using a means for unlocking a self-lockingtether, such as the locking member openings 1654A and 1654B formed inupper surfaces of locking members 1651A and 1651B, for example. This mayallow for readjustment or loosening of a tether clamping assemblyfollowing self-locking of the tether within the assembly.

The foregoing specification has been described with reference to variousembodiments and implementations. However, one of ordinary skill in theart will appreciate that various modifications and changes can be madewithout departing from the scope of the present disclosure. For example,various operational steps, as well as components for carrying outoperational steps, may be implemented in various ways depending upon theparticular application or in consideration of any number of costfunctions associated with the operation of the system. Accordingly, anyone or more of the steps may be deleted, modified, or combined withother steps.

Further, this disclosure is to be regarded in an illustrative ratherthan a restrictive sense, and all such modifications are intended to beincluded within the scope thereof. Likewise, benefits, other advantages,and solutions to problems have been described above with regard tovarious embodiments. However, benefits, advantages, solutions toproblems, and any element(s) that may cause any benefit, advantage, orsolution to occur or become more pronounced, are not to be construed asa critical, a required, or an essential feature or element.

Those having skill in the art will appreciate that many changes may bemade to the details of the above-described embodiments without departingfrom the underlying principles of the invention. The scope of thepresent inventions should, therefore, be determined only by thefollowing claims.

1. A spinal fixation assembly, comprising: a tether configured to engagea spinal feature of a patient's spine, wherein the tether is devoid oflocking teeth; a first coupling piece; a second coupling piececonfigured to be coupled with the first coupling piece; a first passageconfigured to receive a first portion of the tether, wherein the firstpassage is defined by a first surface and a second surface, wherein thefirst passage is configured such that the tether can be clamped inbetween the first surface and the second surface so as to allow thetether to move through the first passage in a first direction and lockthe tether in place so as to at least substantially prevent the tetherfrom moving through the first passage in a second direction oppositefrom the first direction.
 2. The spinal fixation assembly of claim 1,wherein the tether comprises a rectangular shape in cross-section, andwherein the tether comprises opposing surfaces that are at leastsubstantially uniform in roughness.
 3. The spinal fixation assembly ofclaim 2, wherein the opposing surfaces of the tether are smooth.
 4. Thespinal fixation assembly of claim 1, further comprising a second passageconfigured to receive a second portion of the tether so as to define atether loop for engaging the spinal feature.
 5. The spinal fixationassembly of claim 4, wherein the first surface comprises a surfaceroughness greater than a surface roughness of the second surface,wherein the second passage is defined by a first surface and a secondsurface, and wherein the first surface of the second passage comprises asurface roughness greater than a surface roughness of the second surfaceof the second passage.
 6. The spinal fixation assembly of claim 1,wherein the first coupling piece comprises an inner coupling piece,wherein the second coupling piece comprises an outer coupling piece, andwherein the inner coupling piece is configured to be received within theouter coupling piece.
 7. The spinal fixation assembly of claim 6,wherein the first surface is formed on an inner wall of the outercoupling piece, and wherein the second surface is formed on an outerwall of the inner coupling piece.
 8. The spinal fixation assembly ofclaim 7, wherein the first surface comprises a plurality of projectionsconfigured to engage the tether.
 9. The spinal fixation assembly ofclaim 8, wherein the second surface is smooth.
 10. The spinal fixationassembly of claim 8, wherein each of the plurality of projections isdefined by a plurality of elongated grooves formed on the first surface.11. The spinal fixation assembly of claim 1, wherein the first surfaceand the second surface taper relative to a central axis of the firstcoupling piece so as to create a wedge lock for clamping the tethertherebetween.
 12. A tether clamping assembly, comprising: a tetherconfigured to engage a bone; an inner coupling piece; an outer couplingpiece configured to receive the inner coupling piece; and a firstpassage at least partially defined by an inner surface of the outercoupling piece and an outer surface of the inner coupling piece andconfigured to receive the tether therethrough, wherein the first passageis configured such that the tether can be clamped in between the innersurface and the outer surface so as to allow the tether to move throughthe first passage in a first direction and lock the tether in place soas to at least substantially prevent the tether from moving through thefirst passage in a second direction opposite from the first direction,and wherein at least one of the inner surface and the outer surfacecomprises a plurality of projections configured to engage the tether.13. The tether clamping assembly of claim 12, wherein only one of theinner surface and the outer surface comprises a plurality of projectionsconfigured to engage the tether.
 14. The tether clamping assembly ofclaim 12, further comprising a second passage at least partially definedby an inner surface of the outer coupling piece and an outer surface ofthe inner coupling piece and configured to receive a second portion ofthe tether therethrough so as to define a tether loop for engaging thebone.
 15. The tether clamping assembly of claim 14, wherein the secondpassage is configured such that the tether can be clamped in between theinner surface of the second passage and the outer surface of the secondpassage so as to allow the tether to move through the second passage ina first direction and lock the tether in place so as to at leastsubstantially prevent the tether from moving through the second passagein a second direction opposite from the first direction.
 16. The tetherclamping assembly of claim 12, further comprising a cap configured toengage the inner coupling piece.
 17. The tether clamping assembly ofclaim 16, wherein the cap is threaded, wherein the cap is configured toengage a threaded opening formed on the inner coupling piece, andwherein the cap comprises a flange configured to engage the outercoupling piece.
 18. A method for fixation of a tether to an anatomicalfeature, the method comprising the steps of: extending a flexible tetherin a loop around an anatomical feature of a patient; coupling anelongate member with a clamping assembly; threading a first end of theflexible tether through a first passage of the clamping assembly,wherein the first passage is defined by a first pair of opposingsurfaces having distinct surface roughnesses; and threading a second endof the flexible tether opposite from the first end through a secondpassage, wherein the second passage is defined by a second pair ofopposing surfaces having distinct surface roughnesses, and wherein thesteps of threading the first end of the flexible tether through thefirst passage and threading the second end of the flexible tetherthrough the second passage lock the flexible tether in place about theanatomical feature without use of a secondary locking feature to preventa size of the loop from increasing.
 19. The method of claim 18, whereinthe clamping assembly comprises: an inner coupling piece; and an outercoupling piece configured to receive the inner coupling piece.
 20. Themethod of claim 19, wherein the first passage and the second passage areat least partially defined by an inner surface of the outer couplingpiece and an outer surface of the inner coupling piece.
 21. The methodof claim 20, wherein the elongate member comprises a rod, wherein theinner coupling piece comprises a slot configured to receive and engagethe rod, and wherein the step of coupling the elongate member with theclamping assembly comprises engaging the rod with the slot.